Internal combustion engines (e.g., diesel engines, gasoline engines, gaseous fuel-powered engines, and other engines known in the art) typically include a valve train. The valve train includes intake and exhaust valves in a combustion chamber and a mechanism to cause the valves to open and close. The valve train may include a rocker arm assembly having a pushrod that is engaged by a cam lobe positioned on a rotating cam shaft such that the rotation of the cam shaft causes the pushrod to engage a rocker arm and pivot the rocker arm to open and close the intake and exhaust valves. In some instances, lash adjustment features are provided on the valve train to eliminate lash (i.e., the mechanical clearance between valve train components). One type of lash adjustment feature is a hydraulic tappet or a hydraulic lash adjuster (“HLA”), which typically includes mechanical components that cooperate to expand under hydraulic pressure to eliminate lash during one portion of a valve cycle, typically when the valve train is under low load or unloaded, and then assume a hydraulically “locked” or incompressible state during another portion of the valve cycle, typically when the valve train is under high load.
An HLA has been used in a front end of a rocker arm to abut an engine valve, in which the HLA includes a hydraulic lash adjusting arrangement configured to automatically compensate for lash in an engine valve train and a lost motion arrangement configured to inhibit motion (induced in the valvetrain in response to a lift profile of a rotating cam) from being transferred to the engine valve. For example, U.S. Pat. No. 10,294,828, which issued on May 21, 2019, describes an HLA that includes a first plunger that can be expanded by a first biasing means so as to take up slack in the valve train assembly. The HLA also includes a second plunger that allows for the valve to open based on the second plunger's position in relation to the first plunger, but prevents the valve from opening based on another position of the second plunger relative to the first plunger.
An HLA has been placed on a front end of a rocker arm to abut an engine valve, in which an adjustment screw was used to adjust the amount of lift of the engine valve during opening and closing of the engine valve. For example, U.S. Pat. No. 7,493,879, to Fujii et al., which issued on Feb. 24, 2009, describes a rocker arm that includes a receiving member for receiving an HLA, and a restricting part that restricts movement of the receiving member when the engine valve is in a closed state. An adjustment screw is used to adjust the clearance between the restricting part and the receiving member such that there is no variation in the amount of lift of the engine valve even if there are production errors, assembly errors, etc.